“The secret magic of film festivals is that they offer audiences direct communication with the artist,” says Sundance Film Festival Director of Programming Trevor Groth. “You can definitely elevate the impact of your screening by the way you introduce the film and handle the Q&A.” Explains True/False Co-Director and Co-Founder David Wilson, “A great Q&A can really guide your audience, making them feel better about your film and have a clearer understanding of your intentions in making it. And a bad one can hurt that initial buzz that all films depend on at festivals.” “Having access to you, the director, is what makes festivals special for audiences,” agrees SXSW Film Festival Producer Janet Pierson. “And the Q&A will affect how audiences interact with your work and how they’ll talk about it later.”

I agree with some of these points and disagree with others, but overall it's a pretty good tip sheet for handling a festival Q&A.